Although it has long been known that macrolide glycosylation is absolutely essential for antibacterial activity, the megalomicins (which differ from erythromycins solely via an additional sugar attached at C6 of the macrolide) were the first macrolides to display notable antiviral and antiparasitic activities. These new activities, unique to the C6-glycosylated macrolides, are proposed to derive from their ability to cause anomalous glycosylation of proteins essential to viral/parasite development. Given the role of macrolide glycosylation in defining the final antibacterial, antiviral and/or antiparasitic potential of this validated drug scaffold, a simple, rapid, robust method to 'glycorandomize' macrolides may launch the discovery of a wide range of anti-infective drug leads. While macrolide semi-synthesis has allowed for the production of a number of second and third generation macrolide analogs, there is an astonishing lack of differentially-glycosylated analogs - due primarily to the severe limitations imposed by classical glycosylation methodologies. The studies proposed in this application are designed to assess the utility of Centrose's patented technology, known as neoglycorandomization, toward this goal. In this Phase I proposal, we will demonstrate the feasibility of creating differentially-glycosylated ketolide libraries for the identification of anti-infective leads via the synthesis and evaluation of two prototype macrolide neoglycoside series. The 'type A' C6 prototype design is based upon a naturally-occurring C6 O-glycoside precedent (megalomicin) with notable antibacterial, antiviral and antiparasitic activities while, the 'type B' C9 prototype design is based upon non-carbohydrate polyether C9-modifications within second generation macrolides (roxithromycin) with notable antibacterial properties. Both prototypes are based upon a ketolide scaffold known as non-inducers of macrolide resistance (e.g. MLSB) and these modifications are anticipated to enhance binding interactions and possibly influence macrolactone rigidity. Fifty prototype A and 50 prototype B analogs will be generated and specifically screened as antibacterials and antivirals. Given the unique activities of megalomicin, it is anticipated that a combination of antibacterial and antiviral screening of the neoglycorandomized prototype libraries proposed may identify distinct potential leads in one, or possibly both, the antibacterial and antiviral arenas. Depending upon the outcome of this Phase I program, a Phase II is envisioned to encompass studies targeting the mechanism of action and the in vivo efficacy of Phase I lead compounds, library expansion and lead optimization as well as the inclusion of screens targeting specific parasites. The research involves the synthesis of macrolide neoglycosides and their evaluation as anti-bacterial and anti-viral agents, to identify compounds that could be developed into valuable new anti-infective drugs. [unreadable] [unreadable] [unreadable]